[PATCH] ARM64: dma-mapping: preallocate DMA-debug hash tables in core_initcall

[Robin Murphy]

On 16/11/16 09:20, Marek Szyprowski wrote:
> fs_initcall is definitely too late to initialize DMA-debug hash tables,
> because some drivers might get probed and use DMA mapping framework
> already in core_initcall. Late initialization of DMA-debug results in
> false warning about accessing memory, that was not allocated. This issue
> has been observed on ARM 32bit, but the same driver can be used also on
> ARM64.
> 
> This patch moves initialization of DMA-debug to core_initcall. This is
> safe from the initialization perspective. dma_debug_do_init() internally
> calls debugfs functions and debugfs also gets initialised at
> core_initcall(), and that is earlier than arch code in the link order,
> so it will get initialized just before the DMA-debug.
> 
> Reported-by: Seung-Woo Kim <sw0312.kim at samsung.com>
> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>

Acked-by: Robin Murphy <robin.murphy at arm.com>

Cheers Marek - as it happens, the ARM SMMU drivers (and presumably the
Mediatek one) do hit this on arm64 since I added the DMA API support to
the io-pgtable code, I've just been quietly ignoring it in the hope we'd
get the probe-deferral stuff done before anyone else noticed.

Robin.

> ---
> For more details on this issue, see the patch for ARM 32bit arch:
> https://www.spinics.net/lists/arm-kernel/msg542721.html
> https://www.spinics.net/lists/arm-kernel/msg542782.html
> ---
>  arch/arm64/mm/dma-mapping.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index 3f74d0d..8653426 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -538,7 +538,7 @@ static int __init dma_debug_do_init(void)
>  	dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
>  	return 0;
>  }
> -fs_initcall(dma_debug_do_init);
> +core_initcall(dma_debug_do_init);
>  
>  
>  #ifdef CONFIG_IOMMU_DMA
>